Microporous membranes with diverse properties are used in many modern products, including such things as filters, breathable articles, absorbent articles, and medical articles. There are many known ways to manufacture microporous membranes, including a phase separation in a dope layer. By manipulating the conditions that trigger the phase separation, different morphologies can be generated in the resulting microporous membrane, adapting it to the specific needs of the end user.
One of the ways that a phase separation can be triggered is by contacting a dope formulation with a nonsolvent. Methods of making microporous membranes are further described in U.S. Pat. No. 6,736,971 (Sale et al.); U.S. Pat. No. 5,869,174 (Wang); U.S. Pat. No. 6,632,850 (Hughes et al.); U.S. Pat. No. 4,992,221 (Malon et al.); U.S. Pat. No. 6,596,167 (Ji et al.); U.S. Pat. No. 5,510,421 (Dennis et al.); U.S. Pat. No. 5,476,665 (Dennison et al.); and U.S. Patent Application Publication Nos. 2003/0209485; 2004/0084364 (Kools).
Coagulation of dope layers with coagulation baths has been described. Another known method for coagulating dope layers includes introducing a non solvent to the dope layer in the form of a vapor.